Method of Shortening the Time to Compression Mold a Roofing Shingle or Tile and Apparatus for Facilitating Same

ABSTRACT

A method of shortening cycle time required to compression mold shingle or tile is provided, wherein carrier plates are comprised of a surface material and a base, and receive a thermoplastic material, thereon. The roofing material is applied to the carrier plate and the carrier plate is subjected to induction heating, by which its surface material has its temperature raised, without substantially raising the temperature of the carrier plate base, such that the thermoplastic material applied thereto is kept heated in the compression mold. Cooling of the thermoplastic material is by heat transfer from the carrier plate surface material to the carrier plate base, and with both materials having good heat conduction capability. The carrier plate surface material has a high receptivity to being heated by induction heating relative the carrier plate base. The carrier plates are serially delivered through the process, to the compression mold.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 12/636,024 filed Dec.11, 2009, which in turn is based upon U.S. provisional application61/121,925, filed Dec. 12, 2008, from which this application claimspriority.

BACKGROUND OF THE INVENTION

In the art of making roofing shingles and tiles for exterior applicationin the building industry, various approaches have been made towardmaking shingles and tiles that are manufactured, but give the appearanceof being made of traditional natural materials, such as wood cedarshakes, tiles, slate, etc.

In many instances, such shingles and tiles are made of bitumen coatedmat having granules on the exterior surface, with the granules beingprovided in various designs, shades, color configurations, etc., toyield various aesthetic effects.

It is also known, in making roofing shingles and tiles, to mold them tothe desired shape by various molding techniques. The materials that areused in such molding techniques usually include inexpensive fillermaterial, in order to achieve low production costs.

Additionally, molding operations tend to be capital intensive, withrelatively high manufacturing costs, although molding techniques doprovide a high level of definition or dimension control. Also, there isa disadvantage to molding techniques, in general, in that the length ofthe cycle for injecting material into the mold, molding to the desiredshape, and ejecting the shape from the mold is largely a function of thetime required to cool the molten thermoplastic material before it can beremoved from the mold. However, the temperature of the thermoplasticmaterial must be sufficiently high that it can flow and fill the cavitywithin the constraints of the material and equipment (i.e. materialcharacteristics, melt pressures, mold clamping pressures, etc.). Whilemodifications can be made to the materials to help the flowcharacteristics and thereby lower the required melt temperature, andwhile improvements can be made to the mold to increase heat transfer andremoval, cooling remains the longest part of the cycle for theseprocesses. In order to achieve the necessary cooling, the time requiredcauses a lengthening of the manufacturing cycle, which increases thecapital costs of investment in molds and machinery for a requiredoutput, thereby substantially increasing manufacturing costs.

An example of one process for making a shingle or tile is disclosed inU.S. patent application Pub. No. U.S. 2006/0029775, the completedisclosure of which is herein incorporated by reference.

SUMMARY OF THE INVENTION

The present invention is directed to a process of making a shingle ortile having a desired configuration, including a desired outer surfaceconfiguration that, when installed on a roof, has a predeterminedsurface aesthetic for at least that portion of the shingle or tile thatis planned to be weather-exposed in the installed condition, and whereinthe process of molding the shingle or tile is one which achieves shortcycle times for the compression molding portion of the process, in thatthe material that will comprise the shingle or tile is a thermoplasticmaterial, that is applied in a hot, partially molten state, onto apre-heated surface of a carrier plate and the carrier plate is thenplaced in a compression mold in which the shingle or tile is molded,with one surface being stamped during the molding process to have adesired surface aesthetic. The carrier plate includes a top layeragainst which the shingle material is applied and a bottom layer, bothof which layers have heat conduction capability. The top layer has ahigh receptivity to being heated by induction heating, whereas thebottom layer has a lower receptivity to being heated by inductionheating. While in the compression mold, heat from the top layer of thecarrier plate is allowed to be transferred to the bottom layer of thecarrier plate, to cool the top layer of the carrier plate andconsequently to cool the shingle material disposed thereon, so that theshingle material can be more quickly removed from the compressionmolding apparatus than with prior art types of compression molding ofthermoplastic shingles or tiles.

The present invention is also directed to providing a carrier platehaving the characteristics described above.

Accordingly, it is a primary object of this invention to accomplish thecompression molding of thermoplastic, generally polymeric shingles ortiles in a shorter time cycle than with prior art techniques.

It is a further object of this invention to accomplish the above object,using a multi-layer carrier plate, with the layer of the carrier platethat receives the hot, partially molten thermoplastic material thereon,being comprised of a material that has a high receptivity to beingheated by induction heating, whereas the lower layer of the carrierplate has a lower receptivity to being heated by induction heating, suchthat heat transfer from the upper layer to the lower layer of thecarrier plate while the carrier plate is in the compression mold, takesplace more readily, allowing a shorter cycle of compression molding thanwith prior art techniques.

It is another object of this invention to accomplish the above objects,wherein the surface of the shingle material is stamped with a desiredsurface aesthetic, while in the compression mold.

It is yet another object of this invention to accomplish the aboveobjects, wherein a plurality of carrier plates with hot, partiallymolten thermoplastic material applied thereto are serially delivered toan induction heater, and thereafter to a compression molding apparatus.

It is yet another object of this invention to accomplish the aboveobjects, wherein the material that is to comprise the shingle isextruded onto a carrier plate, or onto a plurality of carrier plates tobe serially delivered to the compression molding apparatus.

It is yet another object of this invention to accomplish the aboveobjects, wherein the extruding step applies a double layer ofthermoplastic material to the carrier plate, via a co-extrusionapparatus.

It is a further object of this invention to accomplish the aboveobjects, wherein the carrier plate has an upper layer of surfacematerial that is of substantially higher electrical resistivity than theelectrical resistivity of the lower layer or carrier plate base.

It is a further object of this invention to accomplish the aboveobjects, wherein the carrier plate surface material is a magneticmaterial, and wherein the carrier plate base is a non-magnetic material.

Other objects and advantages of the present invention will be readilyunderstood upon a reading of the following brief descriptions of thedrawing figures, detailed descriptions of the preferred embodiments andthe appended claims.

BRIEF DESCRIPTIONS OF THE DRAWING FIGURES

FIG. 1 is a schematic illustration of an apparatus for accomplishing themethod of this invention, wherein carrier plates are formed by applyinga carrier plate surface material to a carrier plate base, to which thecarrier plate surface material is bonded, and then delivering thecarrier plate thus formed to an induction heater, wherein the carrierplate surface material is heated to a higher temperature than thetemperature of the carrier plate base, via induction heating, andwherein carrier plates thus treated are delivered past an extruder,preferably of the co-extruder type, wherein a hot, partially moltenthermoplastic material, preferably of a polymeric type is applied to thesurface material of the carrier plate, wherein the thermoplasticmaterial that is to be formed into a shingle or tile, is keptsufficiently warm due to its presence against the induction heatedsurface material of the carrier plate, and wherein the carrier platesare serially delivered to a compression molding apparatus, in which thedesired configuration of the shingle material takes place, including astamping of an upper portion of the shingle material to a desiredaesthetic, with the shingle material that is being compression molded iscooled by means of transfer of heat from the shingle material and thecarrier plate surface material, to the carrier plate base, to facilitatecooling of the shingle material while it is in the compression mold, toshorten the required cycle time of the shingle material in thecompression mold.

FIG. 2 is a schematic representation of a carrier plate in accordancewith this invention, with shingle material thereon, and wherein heattransfer takes place between the carrier plate surface material and thecarrier plate base.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1 in detail, it will be seen that a carrier platesurface material 10 that has a high receptivity to being heated byinduction heating and preferably having a high electrical resistivity,is supplied to a carrier plate base 11 and preferably bonded thereto.The carrier plate base 11 has a low receptivity to being heated byinduction heating and preferably a lower electrical resistivity than theelectrical resistivity of the carrier plate surface material 10. Thecarrier plate surface material 10 may be a magnetic material, whereasthe carrier plate base 11 may be a non-magnetic material. Examples ofthe surface material 10 could be materials containing a substantialamount of carbon, steel, tin, or tungsten, or any combination thereof,including alloys thereof. Examples of materials that can comprise thecarrier plate base 11 would be materials containing a substantial amountof aluminum, brass, copper or any combination thereof, including alloysthereof.

Upon bonding the carrier plate surface material 10 to the carrier platebase 11, a carrier plate 12 is formed.

A plurality of carrier plates 12, thus formed, are delivered, by anysuitable means, as shown by the arrows 13, 14, past or through aninduction heater 15. One way of doing so would be to apply the carrierplates 12 to the upper run 13 of a conveyor mechanism 14, being drivenby means not shown, in the direction of the arrow 15, such that carrierplates 12 are serially delivered past an applicator 16 for receipt of apreferably polymeric, hot, partially molten thermoplastic material ontoan upper surface of the carrier plates as shown at 17.

The applicator 16 will preferably be of the extruder type, and morepreferably be of the type having twin screws 18, 20, suitably driven bydrive means 21 to co-extrude the thermoplastic material 17, preferablycomprising two distinct layers, onto the carrier plates 12.

The induction heating apparatus 15 preferably comprises a plurality ofinduction heating coils 22, connected by suitable electric lines 23, 24,to a source 25 of electrical power.

It will be noted that the carrier plate surface material 10 of thecarrier plates 12 is a substantially thinner material than the carrierplate base 11. The induction heater 15 heats the skin or carrier platesurface material 10 more readily than it heats the carrier plate base11.

The material 17 that is extruded onto the carrier plates 12 willpreferably comprise a capstock material 27 and a core material 28. Thecapstock material will generally be a material that comprises at leastthe outer, weather-exposed portion of a shingle or tile, when theshingle or tile is laid up on a roof As such, the capstock material mayhave various characteristics, such as being algae-resistant, beingcomprised of chemicals that provide color retention and/or ultravioletresistance, and perhaps many other characteristics. The core material 28generally need not have such characteristics, and will be thicker, asshown in detail “A” of FIG. 1, than the capstock material 27. The corematerial 28 may optionally have various fillers therein, and willgenerally be of a less expensive material than that of the capstock 27.

The carrier plates 12, with the shingle material 30 thereon, are thenpreferably delivered past a severing device 31, for severing thematerial 30 thereon between adjacent carrier plates 12, via a severingblade 32 or the like, which can be reciprocated upwardly and downwardlyas shown by the double headed arrow 33 of FIG. 1.

Thereafter, another conveyor mechanism such as the conveyor belt 34,assisted by a walking beam type of conveyor 35 or other mechanism,serially delivers the carrier plates 12 with the shingle-formingmaterial thereon, to a compression molding apparatus 36 having avertically movable head 37 thereon, driven upwardly and downwardly asshown by the double-headed arrow 38, so that an upper die 40 thereof canengage against the upper surface of the shingle material, and stamp adesired surface aesthetic thereon, while the lower die 41 supports thecarrier plate 12 with the shingle material thereon.

It will be understood that the upper surface of each carrier plate has apredetermined surface configuration for forming a desired lower surfaceconfiguration for the shingle or tile that is to be molded in thecompression mold 36.

With reference to detail “B” of FIG. 1, it will be seen that apredetermined desired surface aesthetic 42 is formed in the uppersurface of the capstock material 27, by means of stamping, via the upperdie 40, during the compression molding process in the compression mold36.

Normally, compression molding takes a greater amount of time than withthe process in accordance with the instant invention. This additionaltime is usually caused in part because the carrier plates are heated toassist processing. With the present invention, the thermoplastic,preferably polymeric material, adheres to the hot upper surface of thecarrier plate, which is a beneficial feature, because it preventsshifting of the thermoplastic material on the carrier plate during thevarious transfer operations that occur during the process. Also, bykeeping the thermoplastic material in contact with the carrier plate atan elevated temperature, it is possible to produce a higher qualitymolded part, avoiding waves or other undesirable characteristics on theupper surface, and avoiding poorly filled ribs on the bottom of theshingle material during the compression molding process.

Thus, while having at least the upper surface of the carrier plate hotduring the molding process and keeping the thermoplastic material warmduring transfer and molding, such normally hinders the ability to reducethe cycle time, because the majority of the cooling takes place throughthe bottom die 41 on the cavity side of the mold.

In the preferred embodiment both the carrier plate surface material 10and the carrier plate base should have excellent heat conductioncharacteristics. The carrier plate base 11 would preferably be at roomtemperature or some temperature below 200° F. The carrier plate surfacematerial 10 would preferably be at a temperature higher than 200° F.,and certainly no less than that temperature.

The induction heater 15 elevates the temperature of the carrier platesurface material 10, leaving the temperature of the carrier plate base11 at or near its starting point.

By induction heating the carrier plate surface material 10, this layerof the carrier plate keeps the thermoplastic material in its partiallymolten state, thereby at a temperature appropriate for furtherprocessing, including compression molding.

With reference now to FIG. 2, it will be seen that the lines 43simulating heat transfer reflect the cooling of the shingle material 30,as heat is transferred from the carrier plate surface material 10 to thecarrier plate base 11, largely because both layers 10, 11 have good heatconduction characteristics, but that the carrier plate surface material10 can readily be cooled by the transfer of heat to the carrier platebase 11, allowing the cooling of the thermoplastic material 30 thatcomprises both capstock 27 and core 28 to occur more readily, andthereby shorten the cycle time of presence of the shingle material inthe compression mold 36.

It will be apparent from the forgoing that various modifications may bemade in the operation of the process, and in the details of the variouscomponents of the process, as well as in the construction of the carrierplates, and the use of the thermoplastic material that is to be cooledby means of the method of this invention, all within the spirit andscope of the invention as defined in the appended claims.

1. A carrier plate for use in carrying hot, partially moltenthermoplastic material during the processing of that material to becomea roofing element of the shingle or tile type, wherein the carrier platecomprises: (a) a carrier plate base that has heat conduction capabilityand is comprised of a material that has low receptivity to being heatedby induction heating; (b) a carrier plate surface material having heatconduction capability and is comprised of a material that has highreceptivity to being heated by induction heating; (c) with the carrierplate surface material being in bonded relation to the carrier platebase; (d) wherein the carrier plate base is responsive to receiving heattransferred thereto from the carrier plate surface material; and (e)wherein the carrier plate surface material is responsive to being cooledby heat transfer from the carrier plate surface material to the carrierplate base.
 2. The carrier plate of claim 1, wherein the carrier platesurface material comprises a metal material.
 3. The carrier plate ofclaim 1, wherein the carrier plate base is at a temperature below 200°F.
 4. The carrier plate of claim 1, wherein the carrier plate surfacematerial is substantially thinner than the carrier plate base.
 5. Thecarrier plate of claim 1, wherein the carrier plate surface materialcomprises a thin skin.
 6. The carrier plate of claim 1, wherein thecarrier plate surface material is a material of substantially higherelectrical resistivity than the electrical resistivity of the carrierplate base.
 7. The carrier plate of claim 1, wherein the carrier platesurface material comprises a magnetic material and wherein the carrierplate base comprises a non-magnetic material.
 8. The carrier plate ofclaim 1, wherein the carrier plate surface material is selected from thegroup consisting of a material containing a substantial amount of anyof: (i) carbon; (ii) steel; (iii) tin; (iv) tungsten; and (v) anycombination of any of the materials of (i) through (iv).
 9. The carrierplate of claim 1, wherein in the carrier plate base is a materialselected from the group consisting of a material containing asubstantial amount of any of: (i) aluminum; (ii) brass; (ii) copper; and(iv) any combination of any of the materials (i) through (iii).